Pipe coupling device

ABSTRACT

To enable easy and quick coupling of a conduit to the end of a pipe, the device comprises a casing (1,5) having a replaceable, separate casing portion (5) with a resilient sleeve (4a,4b,4c), the radial dimensions of which are adapted to a particular pipe dimension. The sleeve is axially compressible between a stationary abutment (9) and a movable piston (11) having a channel (14) permitting the supply of pressurized fluid through the piston and into the end of the pipe (10a, 10b, 10c).

The invention relates to a pipe coupling device, especially fortemporary connection of a conduit for pressurized fluid to a pipesection.

A pipe coupling device previously known from the U.S. Pat. No. 2,080,271comprises a cylindrical, hollow casing or body to be permanentlyconnected to a conduit for pressurized fluid. The casing is providedwith a follower nut, which is threaded onto the casing and permits theinsertion of two interior gaskets and an intermediate, metallic sleeveradially between the inside of the casing and the outside of the end ofa pipe section fitted into the casing. Each gasket is of a standardcylindrical dimension and is formed of resilient material such as rubberor a rubber-like composition, whereas the intermediate sleeve isprovided with external and internal recesses or shoulders for receivingeach of the gaskets and preventing axial displacement of the latter,when the follower nut is screwed onto the casing. Moreover, the radialdimensions of the intermediate sleeve are chosen in view of thedifference between the internal diameter of the casing and the externaldiameter of the pipe section to be coupled thereto. Thus, uponconnection, the joint will be fluid tight. Moreover, standard casingsand standard gaskets can be used together with radially differentintermediate sleves for connecting pipe sections of different diameters.

However, the purpose of the present invention is to provide a couplingdevice which premits a simpler and quicker coupling operation,especially for temporary connection of the device to various pipesections, having different diameters. Particularly, such a device isintended for use in connection with leakage tests of pipes, fluidvessels, heat exchangers, motor parts and other objects which have to befluid tight. In such a test operation, the object to be tested isnormally supplied with a pressurized fluid for a relatively short periodof time so as to enable the testing of a large number of units in agiven time period.

For this purpose, the coupling device is of the kind comprising a hollowcasing for permanent connection to a conduit for the supply ofpressurized fluid, a resilient sleeve being disposed in the casing andadapted to sealingly engage the cylindrical surface of the end of a pipeto be connected to the casing, and the device is characterized in thatthe resilient sleeve is mounted in a separate casing part, which iseasily replaceable by a corresponding separate casing part having itsown resilient sleeve, the radial dimensions of the respective sleevebeing adapted to a particular pipe dimension, and that the sleeve, uponmounting of the separate casing part, is axially compressible between astationary abutment and a piston, which is operable for axialdisplacement in the casing and provided with a channel permitting thesupply of said pressurized fluid through said piston and into said pipesection.

It has turned out that the inventive device, apart from permitting aneasy and quick coupling operation when shifting from one pipe dimensionto another, has the advantage that the axial holding power, by frictionbetween the radially expanded sleeve (upon axial compression) and thesurface of the pipe, is maintained approximately at the same high levelirrespective of the various pipe dimensions, in spite of the fact thatthe axial force, which is exerted by the pressure of the fluid and tendsto axially separate the pipe from the coupling device, is heavilyincreased when shifting from a smaller to a greater diameter of thepipe.

The invention is explained further below with reference to the drawingsillustrating an exemplary embodiment of the inventive device.

FIG. 1 shows in axial section a pipe coupling device according to theinvention and the end of a pipe section to be connected thereto;

FIG. 2 shows a device corresponding to that of FIG. 1 but having acasing part with a resilient sleeve of a larger internal diameteradapted to fit onto a pipe section having a larger diameter than that ofFIG. 1;

FIG. 3 shows a device corresponding to that of FIG. 1 and 2 but beingadapted to a still larger diameter;

FIG. 4 is a diagram illustrating an essential advantage of theinvention.

The pipe coupling device shown in FIGS. 1 to 3 comprises essentially acylindric casing 1, preferably made of metal, such as aluminium orsteel, having an end wall 2 at one end and an internal thread 3 at theother end. In accordance with the invention, a sealing sleeve 4a,4b and4c, respectively, of a desired dimension is replaceably disposed in thecasing 1, namely in a separate cylindrical casing portion 5 which, bymeans of an external thread 6, is threaded into the remaining portion ofthe casing 1 in the thread 3. The sealing sleeve 4a, 4b, 4c is made ofelastic material, such as natural or synthetic rubber and is fittedbetween two rigid annular washers or plates 7a and 8a, 7b and 8b, 7c and8c, respectively, the radical dimensions of which correspond essentiallyto the dimensions of the sealing sleeve 4a,4b and 4c, respectively,though the internal diameter thereof is somewhat larger than that of thesealing sleeve. The annular plate 8a, 8b, 8c situated adjacent the freeend of the casing portion 5 is seated against an internal shoulder orflange thereof, whereas the inner plate 7a,7b,7c situated at theopposite end of the sealing sleeve 4a,4b,4c is axially displaceablewithin the casing portion 5.

In order to effect an axial compression and, as a result thereof, aradial expansion of the sealing sleeve 4a,4b, 4c upon fitting the pipecoupling device onto the end of pipe 10a,10b and 10c, respectively, tobe connected sealingly, a piston 11 is axially movable in thecylindrical casing 1. At one end, the piston 11 is provided with anarrower portion 12, which protrudes axially through an opening in theend wall 2 and is sealed relative to the latter by means of a sealingring 13 (FIG. 1), e.g. an O-ring inserted into a corresponding annulargroove in the surface defining the opening of the end wall 2. A central,cylindrical channel 14 extends axially through the piston 11 from oneend thereof to the other. At the protruding, narrower piston portion 12a pipe fitting 15 is permanently screwed into a thread at the outer endof the central channel 14, so that the channel 14 and the central hollowspace of the sealing sleeve 4a,4b,4c communicate with a conduit 16connected to the pipe fitting 15. The conduit 16 is preferably aflexible tube or hose connected to a fluid source (not shown) for thesupply of pressurized fluid in the form of gas or liquid.

The inner, radially wider portion of the piston 11 forms the pistonitself and is actuated by the pressure of a fluid present in the annularspace defined between, on the one hand, the external surface of thepiston 11 and, on the other hand, the inside of the casing 1 and itswall 2 at one side (to the left in FIG. 1) of a piston sealing ring 17.Via a conduit 18 and a port 19 in the end wall 2, a desired workingpressure can be applied in the annular space so as to displace thepiston 11 axially towards the sealing sleeve 4a, 4b, 4c, which underaxial compression will expand radially and inwardly against the externalsurface of the pipe section 10a,10b,10c. As a result, one obtains afluid tight seal and a frictional engagement, whereby the couplingdevice is held firmly onto the pipe section against the action of theaxially separating force exerted by the pressurized fluid.

An essential advantage of the pipe coupling device according to theinvention is that one can use the same casing 1, piston 11 and conduit15, 16 and 18,19, respectively, for a substantial range of the diameterof the pipe section, as illustrated by the pipe sections 10a, 10b and10c, whereby only the casing portion 5 and the sealing sleeve 4a,4b,4cneed to be replaced as a unit (including also the plates 7a and 8a, 7band 8b, 7c and 8c, respectively) when shifting to another dimension ofthe pipe section.

Moreover, tests have shown that the axial holding force due to thefriction between the sealing sleeve 4,4b,4c and the pipe section10a,10b,10c is favourably related to the axially separating forceexerted by the pressure in the conduit 16. Thus, the holding forceincreases when increasing the pipe diameter (and the diameter of thesealing sleeve) within a rather large diameter region. This is shown inFIG. 4, which is a diagram illustrating the maximum working pressure (atwhich the sleeve 4a,4b,4c barely keeps its grip around the end of thepipe) as a function of the pipe diameter. Within the interestingdiameter region D₁ (15 to 35 mm), particularly within the region D₂ (20to 30 mm), the curve is relatively flat, i.e. the maximum workingpressure is essentially independent of the diameter of the pipe. Thus,it is possibly to use a constant pressure of the fluid, especially air,by which the piston 11 is actuated via the conduit 18 and the port 19.

In principle, the pipe coupling device according to the invention can bemodified for internal sealing of the pipe section 10a,10b, 10c, in whichcase the piston 11 is preferably provided with a portion protruding fromthe casing portion 5, whereas the sealing sleeve 4a,4b,4c is to beinserted between the outer end of the casing portion 5 and an externalring flange or collar on the protruding portion of the piston.

Furthermore, the interchangeable mounting of the casing portion at theremaining part of the casing can, of course, be achieved by other meansthan the threads, e.g. by a bajonet-mount, a snap locking device or thelike.

The sealing sleeve 4a,4b,4c may also be compressed in another way thanexerting pressure on the piston. e.g. by means of a lever mechanismwhich is manually operable.

Moroever, it is possible to make use of the threads 3,6 of the casingportions of the embodiment shown in FIGS. 1 to 3 in such a way that thethread 6 is screwed only partly into the thread 3, whereas the piston 11is provided with a stop face 20 co-operating with the inner end surface21 of the casing portion 5, so as to form a stop means for the piston11. If so desired, a rather high operating pressure could then be used,and the radial expansion of the sealing sleeve 4a,4b,4c can becontrolled by an axial adjustment of the casing portion 5 relative tothe casing.

I claim:
 1. A pipe coupling device for connecting a conduit to a pipesection, said device comprising: a hollow casing, a resilient sleeve insaid casing with a radially inner surface for sealingly engaging saidpipe section, and a tubular element axially moveably arranged in saidhollow casing for axially compressing and radially expanding said sleevesaid casing including abutment means thereon for retaining said tubularelement and resilient sleeve therewithin and for providing abutmentmeans for said resilient sleeve during said compression thereof, saidtubular element being adapted to be permanently connected to saidconduit for the supply of pressurized fluid axially through the interiorof the tubular element into said pipe section, said hollow casingcomprising a readily detachable unit including a separate casing portionand said sleeve and being easily replaceable by a similar unit having asleeve with a different radially inner surface adapted to a differentpipe section dimension, and said tubular element being a piston with aradially widened portion forming a piston surface to be exposed to anactuation fluid for axially displacing said tubular element duringcoupling operation.
 2. A pipe coupling device as defined in claim 1,wherein said detachable unit also comprises rigid ring plates insertedaxially on opposite sides of said sleeve, the radial dimensions of saidtwo ring plates corresponding essentially to the radial dimensions ofsaid sleeve.
 3. A pipe coupling device as defined in claim 1 or 2,wherein said separate casing portion of said detachable unit threadedlyengages the remainder of said casing, and said piston and said separatecasing portion having co-operating surfaces forming a stop means forsaid piston.